This invention involves the casting of nickel or cobalt base super alloys and particularly it is useful in the casting of alloyed parts or articles which must be of a high degree of uniformity in alloy composition and cast to precise dimensions to reduce or eliminate the necessity for any significant amount of finish machining. It is particularly useful in systems in which the size of the charge provided for each mold is precisely the volume of alloy necessary to cast the finished part or parts. Such systems include ones using a melting unit capable of discharging molten metal through a controlled opening and certain directional solidification "DS" casting processes and single crystal processes. Examples of the type of parts for which this particular system is useful are in the casting of alloyed turbine blades, wheels for superchargers and/or turbochargers. Because of the high centrifugal speeds of these products and the high stresses of their operation, it is essential that the parts all be of uniform composition, shape, size and weight.
It has been conventional practice to prepare a master alloy charge for remelt casting of precise parts such as turbine blades by melting the various elements which form the composition of the alloy and then casting them in a pipe or similar mold. After the cast alloy has cooled and solidifed, it is removed from the pipe. Frequently, the removal of the alloy from the pipe is a very difficult, slow and unsatisfactory procedure. Further, the cast product produced from the pipe is not uniform in cross section and, therefore, must be machined by either turning or grinding to render it uniform in cross section and to render it absolutely straight. This has been necessary also to give it a proper external finish whereby throughout its length the charge was of uniform characteristics. Machining is also necessary to remove all slag and scale which, if not removed, would modify the composition and thus the resulting material would not have a true net chemical composition by weight percent. This procedure is expensive, time consuming and, unless great care is taken, lacks the desired uniformity for accurately charging the mold in the final casting procedure.